1. Field of the Invention
An electrosurgical instrument comprising a work implement coated with a plurality of layers of different compositions to reduce sticking and tissue charring when in use.
2. Description of the Prior Art
Electrically powered instruments such as coagulation forceps, suction cauteries, electrode cautery tips and blade electrodes are well known. Such medical instruments are used in procedures that involve cutting and other contact with flesh or tissue. For example, surgical blade electrodes are utilized to reduce bleeding by cauterizing the exposed tissue. Typically, a blade electrode is affixed to a handpiece activated for passing electrical energy into the blade electrode to transmit radio-frequency electrical energy to the flesh or tissue to cauterize the site. Other electrosurgical devices are similarly designed. Unfortunately, sticking or charring of the cauterized tissue and blood on the medical implement can occur.
Various coatings covering a portion or the entire working surface have been used on the cauterizing instruments to render the surfaces less adherent. Coating the entire surface greatly reduces the problem of sticking and charring but results in dull cutting edges. On the other hand, coating only a portion of the working surface results in charring and sticking on the bare portion.
Much of the prior art has reduced the adherence of tissue to electrosurgical instruments. However, it has been necessary to coat essentially the entire surface that comes in contact with the flesh or tissue and the like or not exceed a low level of metallic islands in order to achieve an acceptable level of charring and adherence. Moreover, the addition of a coating which completely eliminates metallic contact with tissue resulted in some undesired dulling of these electrosurgical instruments which are also used for cutting.
U.S. Pat. No. 5,197,962 describes an electrosurgical instrument for causing hemostasis having a first predetermined region for contact with flesh or tissue. At least a portion of the predetermined region by a composite coating consisting essentially of a nickel-phosphorous matrix having particles of polytetrafluoroethylene distributed substantially uniformly therethrough.
U.S. Pat. No. 4,785,807 shows an electrosurgical knife including a stainless steel blade having an abraided or etched surface, a first coat of primer material is applied over the blade where the surface of the primer material is also abraided or etched. A second coat of non-stick fluorinated hydrocarbon material is applied over the coat of primer material having a total thickness of about three mils permitting conduction of radio-frequency electrical energy from the blade through the coatings to the tissue being cut.
The method of manufacturing the electrosurgical knife disclosed in U.S. Pat. No. 4,785,807 is shown in U.S. Pat. No. 4,876,110.
U.S. Pat. No. 5,100,402 teaches a laparoscopic cauterization electrode for use with an electrical power source for deep surgical operations through an opening in a body such as deep thorax, abdominal perineal, deep rectum, deep gynecological and similar deep body operations. The laparoscopic cauterization electrode comprises an electrically conductive electrode shaft for insertion through the body opening having a proximal end connected to the electric power source and a distal end having teflon-coated operative tip.